The Hubble Space Telescope has confirmed the beginning of a new “speaking season” on Saturn. These are the times of the Saturn year gathering around the equinoxes, when mysterious radial points resembling the fingers of a wheel appear in the planet’s rings. Exactly what causes the wires is unknown, but their reappearance with the Hubble Planetary Observing Program will provide an opportunity to study them in greater detail. Scientists hope to understand not only what the railings are, but also why they only appear seasonally, disappearing and reappearing at certain times of Saturn’s year.

“Thanks to the Hubble OPAL program, which has created an archive of data on the outer planets of the Solar System, we’ll have more time than ever to study the speakers of Saturn this season,” said NASA planetary scientist Amy Simon.

We first discovered Saturn’s lattice in images taken from two Voyager probes that passed by Saturn in 1980 and 1981, respectively: temporal lines and dots, typically appearing as radial features, that move with the rings as they orbit Saturn. Further observation and analysis revealed even more oddities. Strands often appear dark at the top, but are often bright at the bottom and are not always present.

Typically, the railings appear only in the spring and autumn of Saturn, during the eight-year period when the equinoxes are centered, and disappear during the summer and winter for the period when the solstices are centered. Saturn is very different from Earth in many ways, but in some ways these two planets are similar. Both have a significant axial tilt with respect to their orbital planes; For Earth, this tilt is 23.45 degrees, and for Saturn – 26.73 degrees.

This tilt gives the Earth its seasons. As our planet orbits the Sun, the Northern and Southern Hemispheres receive more or less sunlight depending on whether they are tilted towards or away from the Sun. The point where the slope is deepest is during the summer and winter solstices. It is known as the equinox, which occurs in spring and autumn when there is the least slope with respect to the sun. Saturn has this too, but it also has rings and they are also tilted. Saturn’s rings are inclined towards the Sun on solstice days, and on equinox days the rings are arranged almost like ribs.

Because Saturn is much farther from the Sun, its year is also longer. It takes 29 years for Saturn to orbit the Sun, and each season takes about 7 years. Decades of observations show that fingers usually begin to appear about four years before the equinox. The next equinox on Saturn will be in 2025, so the start of the “speaking season” was predicted in 2021.

“Despite years of excellent observations by the Cassini mission, the exact onset and duration of the hurricane season is still unpredictable, just as predicting the first storm of the hurricane season,” Simon said.

Hubble is running a campaign to observe the outer planets of the Solar System, the Legacy of Exoplanet Atmospheres (OPAL) program, so Simon and his team used this data to look for fingerprints from Hubble’s 2021 and 2022 observations. skewers appeared in 2021 according to the schedule. The team then tracked the spokes for an 11-hour period with data from September 2022. Talking season is well and truly underway.

Scientists have some ideas about the causes. Data from several missions, including Voyager, show that the gratings themselves are made up of dust particles from the individually rising rings that are separated from the ice floes in the rings. And it could be Saturn’s magnetic field that made them do it.

When the solar wind interacts with Saturn’s magnetic field, it creates an electrically charged environment, somewhat like a giant Van de Graaf generator. This could affect the charged dust particles in Saturn’s rings, causing them to electrostatically stick together and temporarily create denser dust patches in the rings. But it’s not entirely clear whether this really happens or why it’s a seasonal phenomenon. Over the next few years, Hubble data could help scientists unravel the mystery.

“The Hubble OPAL program will continue annual observations of Saturn as long as the object is operational,” the researchers write, “and soon the speakers will also be clearly visible to ground-based telescopes.”